In Yasothon if you stay in the city center it is easy to get to the location of the rockets. It may be hard to find a hotel in the city now. I looked on Agoda yesterday and did not see anything in the center.
I have not been to Kutwa, Kuchinari so have no idea.
The schedule I got from my hotel last year said the rockets would start at 7 in the morning. I think they did not really get going until about 9. I attached the schedule from last year, sorry I only have the Thai version and had to run everything through google translate.